Hydraulic lash adjusters



Jan. 7, 1958 O 1 2,818,844

HYDRAULIC LAsl-i ADJUSTERS Filed Sept. 15, 1956 p -H mw w W m WE 7 W A p w 6 United States Patent HYDRAULIC LASH ADJUSTERS George Wood, Southfield Township, Mich. Application September 13, 1956, Serial No. 609,560

4 Claims. (Cl. 123-90) This invention relates to hydraulic lash adjusters for automatically taking-up the play inherent in valve trains of internal combustion engines.

Internal combustion engine poppet valve operating mechanisms generally include a train of several elements which transfer motion from the valve actuating cam to the valve stem to open the valve against spring pressure constantly urging the valve to its closed position. Inasmuch as the operating clearances in the valve train vary in accordance with engine operating temperature variations and because of wear between the several elements of the valve train, it has been a generally accepted practice to employ lash adjuster means in the valve train to automatically take-up and compensate for the variable clearances therein. 1

Although there have been a number of types of h draulic lash adjusters employed in internal combustion engines, none have proven entirely satisfactory because of their malfunctioning as a result of gummy deposits which accumulate therein. The deposit of such gummy substances in hydraulic lash adjusters is known in the art as varnishing. Also, prior art hydraulic lash adjusters are generally of complex construction, expensive to manufacture and difficult to service.

With the foregoing in view, the primary object of the invention is to provide an inexpensive, simplified and improved hydraulic lash adjuster for valve trains of internal combustion engines which performs its function with a minimum of possibility of varnishing under normal engine operating conditions, which requires a minimum of service, and which alleviates the frequent periods of malfunctioning that characterize many of the prior art devices.

Other objects of the invention will become apparent by reference to the following detailed description taken in connection with the accompanying drawing, in which:

Fig. l is a vertical sectional view of a hydraulic lash adjuster embodying the invention operatively mounted in an engine block, the said hydraulic lash adjuster being shown in the position assumed by it when the engine valve is closed.

Fig. 2 is a vertical sectional view similar to Fig. 1 except that the hydraulic lash adjuster is shown in the position to which it is moved when the valve timing cam has fully opened the engine valve.

Fig. 3 is an enlarged sectional view through the upper end of the lash adjuster piston.

Fig. 4 is a cross sectional view taken on the line 4--4 of Fig. 3.

Referring now to the drawings wherein like numerals refer to like and corresponding parts throughout the several views, a hydraulic lash adjuster illustrating the invention is reciprocatingly mounted in a bore 11 of the block 12 of an internal combustion engine, the said bore 11 being axially aligned with a push rod or valve stem 13 and is disposed normal to the longitudinal axis of the earn shaft 14 over an engine valve operating cam 15 ice thereof. As the cam shaft 14 rotates, the cam 15 raises the hydraulic lash adjuster 10 from the position shown in Fig. 1 to the position shown in Fig. 2 whereby to move the push rod 13 upwardly and open an engine valve; the said push rod 13 being a part of an engine valve train generally employed in internal combustion engines usually consisting of the push rod 13 and a rocker arm which opens a spring loaded closed engine valve responsive to the movement of the push rod 13 by the cam 15.

inasmuch as engine valve and valve train construction is conventional and is not a part of the instant invention, it is not shown in the drawing. However, it is important to note that the engine valve spring operating through the valve train constantly urges the push rod 13 in the direction indicated by the arrow 1300 thereon. Because of necessary clearances in the engine valve train required to permit expansion and contraction therein occasioned by extreme operating temperature changes in the engine, the hydraulic lash adjuster 10 is employed automatically and continuously takes up these clearances or lash in the valve train.

Referring now specifically to the improved hydraulic lash adjuster 10, it consists of a cylinder 20 axially bored from its upper end at 21 to reciprocatingly accommodate a piston 22 and counterbored at 23 to receive a compression spring 24 telescoped over the depending stem 220 of the piston 22. The lower end 200 of the said cylinder 20 is preferably slightly domed to ride on the cam 15 as shown in Figs. 1 and 2. The lower end of the stem 220 seats on the seat 230 at the base of the counterbore 23 if and when the piston 22 is urged to refusal within the cylinder 26. The said compression spring 24 also seats on the said seat 230 as shown in Figs. 1 and 2 and abuts against the annular shoulder 221 of the piston 22 located at the upper end of the stem 220 thereof. The top of the said piston 22 is preferably cupped at 222 to accommodate the substantially semi-spherical end of the push rod 13.

The upper end of the cylinder 20 is counterbored at 25 and tapered at 26 to provide an exhaust valve port 27 and an oil reservoir 28 respectively. The outer wall of the said cylinder 20 is circumferentially grooved at 29 and horizontally bored at 30 to provide a pressure inlet to the main bore 21 thereof from a pressure oil port 31 in the engine block 12 to which oil under pressure from the usual engine oil pressure source is continuously available during the running of the engine.

The piston 22 is axially bored at 32 from its lower end to provide a main longitudinal fluid passage therein extending from the bottom of the depending stem 220 of the said piston 22 to a short distance from the upper end thereof. A counterbore 33 is provided at the upper end of the central axial bore 32 and transverse bleed passages 34 extend radially outwardly from the said counterbore 33. A valve seat 35 for a valve ball 36 is formed at the transition between the bore 32 and the counterbore 33, which valve 36 closes and opens under operating conditions of the hydraulic lash adjuster as hereinafter described. When the ball valve 36 is off its seat 35, it is held in a position proximate thereto by such means as a ball retainer pin 37 pressed into a suitably located transverse bore 370 in the piston 22, see Figs. 3 and 4.

The piston 22 is provided with transverse outlet passages 38 communicating between the central axial bore 32 thereof and an upper circumferential groove 39 therein so located as to cooperate with the exhaust port 27 of the cylinder 20 to permit a free flow of oil through the piston 20 when the engine valve is in its closed position and the hydraulic lash adjuster assumes its position shown in Fig. 1.

The said piston 22 is also provided with a central circumferential groove 40 therearound located to register with the oil pressure inlet 30 through the wall of the cylinder 20 when the engine valve is in its closed position and the hydraulic lash adjuster assumes its position shown in Fig. l. A diametrically disposed bore 41 communicates between the said circumferential groove it? of the piston 22 and the central axial bore 32 thereof One or more pressure relief passages 42 are provided through the side of the stem 220 of the piston 22 near the bottom thereof, which relief passages 42 communicate between the counterbore 23 in the bottom of the cylinder 26 and the axial bore 32 of the said piston 22 substantially at the bottom of its depending stem 220.

During the operation of the hydraulic lash adjuster 10, it normally assumes the position shown in Fig. 1 when the engine valve is closed, in which normal engine valve closed position the domed bottom 2% of the cylinder 20 of the hydraulic lash adjuster rides on the base circle of the cam 15. In this normal engine valve closed position, the combined spring pressure of the compression spring 24 and the hydraulic pressure within the cylinder chamber A acting on the lower end of the piston 22 takes up all lash in the valve train from the cam 15 to the engine valve, not shown. In this normal engine valve closed position, oil under pressure enters the chamber A of the cylinder from the oil pressure port 31 in the engine block 12 through the oil groove 29 and the pressure inlet 39 of the cylinder 29, and through the oil groove 40, diametrically disposed bore 41 and the axial bore 32 of the piston 22. Simultaneously oil under pressure passes out of the upper portion of the axial bore 21 of the piston 22 through relatively small transverse outlet passages 33 communicating with the oil groove 39 of the piston 22 from whence it spills out of the exhaust valve port 27 through the reservoir 28 into the engine oil pan, not shown.

As the engine cam shaft 14 turns, the lobe 1599 of the cam 15 lifts the hydraulic lash adjuster 10 and the push rod 13 of the engine valve train and opens the engine valve, not shown, whereupon the cylinder 20 of the said hydraulic lash adjuster ltl assumes a position as indicated in Fig. As the cylinder 2% moves upwardly to its engine valve open position, the piston 22 is moved downwardly in respect thereto as shown in Fig. 2. The relationship between the circumferential grooves 39 and 49 of the piston 22 and the ports 27 and 30 respectively is such that, as the piston 22 moves downwardly into the cylinder 21), the pressure inlet port 30 is closed slightly ahead of the closing of the exhaust port 27 whereby to cause oil to be moving out of the exhaust port 27 as it finally closes. Oil under pressure in the bore 32 of the piston 22 causes a pressure closing of the ball valve 36, and, when the inlet port 30 and the exhaust port 2-7 are closed oil is confined in the cylinder chamber A and in all of the oil passages of the piston 22 whereupon the cylinder 20 and the piston 22 become temporarily hydraulically locked into a unit.

As the cam lobe 1506 permits the hydraulic lash adjuster to become hydraulically unlocked, the compression spring 24 initially moves the piston 22 upwardly in respect to the cylinder 24) until the exhaust port 27 and inlet port 31 sequentially open whereupon both hydraulic and spring pressure within the hydraulic lash adjuster ll) takes up the lash in the valve train between the cam 15 and the engine valve, not shown. During this sequential opening of the exhaust port 27 and the inlet port 31, the ball valve 36 unseats to relieve vacuum within the cylinder chamber A. Should the engine happen to stop with its cam 15 holding the engine valve open, the pressure from the engine valve spring would constantly urge the piston 22 downwardly within the cylinder 20, and, if any minute leakage should occur between the cylinder 20 and the piston 22, the lower face of the depending end 220 of the piston 22 may seat upon the seat 239 at the bottom of the counterbore 23 of the cylinder 20. Whenever the engine is again started and the cam 15 is turned, the ball valve 36 unseats and the relief passages 42 permit oil to flow momentarily from the axial bore 21 into the chamber A whereupon the piston 22 becomes free to be moved upwardly by the compression spring 24, and the normal cycle of operation of the hydraulic lash adjuster 10 begins forthwith, during which operating cycle there is a piston reciprocation and a movement of fresh engine oil into and out of the cylinder and piston 22.

The improved hydraulic lash adjuster 10 provides a relatively anti-varnishing construction which operates continuously and quietly over extremely long periods of time without the necessity of frequent adjustment of valve train clearances or other service, and, due to its simple, rugged construction, it is economical to manufacture, assemble and service.

Although but a single embodiment of the invention has been disclosed and described in detail, it is obvious that many changes may be made in the size, shape, arrangement and proportions of the various elements thereof, all without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. In a hydraulic lash adjuster for the cam actuated valve train of an internal combustion engine having lash adjuster bores in the block thereof each with an oil pressure port communicating therewith, said hydraulic lash adjuster being slidable axially in a lash adjuster bore as an element of said valve train and comprising a cylinder having one closed end and one open end, a piston reciprocaoly mounted in said cylinder forming a pressure chamber in the closed end thereof, a compression spring in said pressure chamber constantly urging said piston toward the open end of said cylinder, the said piston having an axial bore and counterbore therein communicating with said pressure chamber, said piston having a bleed port communicating with said counterbore and a valve seat formed at the point of transition between said axial bore and said counterbore, a ball in said axial bore disposed adjacent said seat closing off said bleed port responsive to oil pressure within said piston and said pressure chamber, the said cylinder having an exhaust port formed at the upper end thereof, the said piston being formed with circumferential grooves and transverse bores therein communicating with its axial bore whereby to function as a valve spool and provide pressure oil flow from said pressure port through said piston and cylinder when the engine valve controlled by said valve train is closed and to hydraulically lock the said piston in said cylinder in the position assumed thereby when said engine valve is opened by said cam actuated valve train.

2. A hydraulic lash adjuster as claimed in claim 1 wherein the circumferential grooves in said piston are so located in respect to the oil pressure port and the exhaust port that the oil pressure port closes slightly before the closing of the said exhaust port.

3. A hydraulic lash adjuster as claimed in claim 2, wherein a relief port is provided between the axial bore of said piston and the closed end of said cylinder adjacent the inner end of said piston.

4. In a hydraulic lash adjuster for cam actuated valve trains of internal combustion engines, a cylinder having one closed end and one open end slidable in a bore in the block of said engine in communication with an oil pressure port therein, a piston reciprocable in said cylinder forming a pressure chamber in the closed end thereof, a spring in said pressure chamber constantly urging said piston axially toward the open end of said cylinder, said cylinder and said piston being formed to cooperate as spool valve means to establish alternately an axial endwise hydraulic thrust relationship therebetween and a hydraulically locked relationship between said piston and cylinder responsive to cam actuated movement of the 5 valve train, the said spool valve means being arranged to provide an inlet port to said pressure chamber and an outlet port therefrom, the said inlet port being located to close slightly before the closing of the outlet port responsive to axial movement of said spool valve means to close said ports, the said piston having a relief passage therein communicating with said pressure chamber,

References Cited in the file of this patent UNITED STATES PATENTS Randol Apr. 5, 1955 Engemann Jan. 31, 1956 

